title: Desorption of ionic species from ice/graphite by femtosecond XUV free-electron laser pulses.
abstract: We report results of laser desorption from water ice surfaces using XUV pulses from the free-electron laser in Hamburg (FLASH). This XUV to soft x-ray FEL provides femtosecond pulses at 20-200 eV photon energy with pulse energies up to 100 µJ. The interaction of this intense soft x-ray radiation with ice (H2O, D2O) adsorbed on highly oriented pyrolytic graphite (HOPG) yields the desorption of various ions, particularly H (+) (D (+) ), O (+) , O2 (+) and others. For H (+) and O (+) ions linear desorption yields are observed, while for O2 (+) a highly nonlinear desorption yield with n = (2.5 ± 0.2) is found. Kinetic energies of 1.8 eV, 559 meV and 390 meV for H (+) , O (+) , and O2 (+) , respectively, account for only a small part of the available excess energy.
authors.affiliation: Physikalisches Institut, Westfälische Wilhelms-Universität Münster, Wilhelm Klemm Strasse 10, 48149 Münster, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Siemer
authors.forename: T
authors.initials: T
authors.lastname: Hoger
authors.forename: M
authors.initials: M
authors.lastname: Rutkowski
authors.forename: R
authors.initials: R
authors.lastname: Treusch
authors.forename: H
authors.initials: H
authors.lastname: Zacharias